At the present stage, the image or video captured by the camera can record the color projection of the real world on a two-dimensional plane, but fails to reflect the three-dimensional structure of a real scenario. The depth image can show depth of each point in the scenario, i.e., each pixel in the depth image records the distance from one certain point in the scenario to the XY plane on which the center of the camera located. The depth image has very wide applications in the field of 3D measurement and man-machine interaction. At present, depth images of the scenario can be acquired by the depth camera.